1. Field of the Invention
The present invention relates to an ink jet printer for forming an image on a recording paper sheet with a recording head mounted on a reciprocating carriage.
2. Description of the Related Art
Conventionally, there has been used an ink jet printer which forms an image on a recording paper sheet by discharging ink drops from a recording head while reciprocating a carriage which mounts the recording head thereon in a direction (hereinafter referred to as a main-scanning direction) perpendicular to a recording paper sheet conveying direction (hereinafter referred to as a sub-scanning direction). Such ink jet printer is constituted that an image can be formed on a recording paper sheet of various sizes, for example, from A4 size to postcard size.
However, although such a conventional ink jet printer is constituted to form an image on the recording paper sheet of, for example, of A4 size at a maximum one by one, even when an image is formed on a small recording paper sheet such as a postcard, the recording paper sheet is fed from a paper sheet feed tray one by one, an image is formed on the recording paper sheet and the printed recording paper sheet is ejected to a paper sheet exit tray. Thus, especially when images are formed on a lot of postcards, it takes a long time to complete image formation. In such an ink jet printer, to miniaturize an ink jet printer main body, the number of recording paper sheets which can be mounted on the paper sheet feed tray is limited. Thus, when images are formed on a lot of recording paper sheets, it is necessary to frequently fill the paper sheet feed tray with the recording paper sheets, thereby causing inconvenience to the user.
For example, Unexamined Patent Publication No. 6-340137 describes a laser printer in which printing speed is improved by processing some printing operations in parallel. However, in the laser printer, recording units for carrying out printing are provided in parallel. Thus, the laser printer has a complicated configuration and requires high costs.